The present invention relates in general to electronic circuits and in particular to an electronic circuit for generating delays using a delay locked loop.
The growth and maturity of the electronics industry has led to a variety of products that have changed the way people live and work. Electronic circuits are currently the dominant technology for creating products that move and shape information. In the world of electronics, information is typically represented by zeros and ones. Electronic representations of zeros and ones are referred to as digital signals. Electronic circuits process digital signals to perform a wide variety of functions.
However, as the electronics industry continues to grow, there is an ever increasing demand on the amount of information that must be processed by electronic circuits. Accordingly, the speed at which these electronic circuits operate has continually increased. An electronic circuit's processing speed is determined by the frequency of the signals. For example, some electronic circuits carry out a processing operation on each rising edge of a system clock. These circuits are referred to as “synchronous” circuits. Therefore, the processing speed of the circuit will be determined by the frequency of the clock.
As the operating frequencies of electronic circuits continue to increase, the timing relationships between signals can severely limit the performance of the system. For example, if a clock signal triggers the execution of a function requiring two digital input signals, the function will produce an erroneous result if the clock signal triggers the function before one or both of the digital inputs are available. One circuit commonly used to control the timing relationships between signals is a delay circuit. A delay circuit receives a digital signal on an input terminal and produces the signal on an output terminal after a predetermined period of time (i.e., after a time delay). Delay circuits may be used to delay signals for a variety of reasons depending on the particular application. However, as operating frequencies increase, delay circuits must provide ever increasing levels of precision to ensure accurate timing of the signals. Accordingly, there is a need for improved delay circuits that can provide precision delays.